Rational Method Peak Runoff
Rational Method Peak Runoff
The Rational Method estimates peak runoff from a catchment’s area, rainfall intensity and a runoff coefficient — the staple of drainage design.
The peak runoff is Q = C·i·A. where C is the runoff coefficient, i the rainfall intensity and A the catchment area.
Inputs
C := 0.7=0.7
i := 0.00003 m/s=3e-05 m/s
A := 10000 m^2=10000 m^2
Apply the Rational Method.
Q := C·i·A=0.21 m^3/s
Results
The runoff coefficient captures how much rain runs off versus soaks in — high for pavement, low for grass. This peak sizes the drainage pipes.
Assumptions & limitations
- Rational Method assumptions.
- Uniform intensity over the time of concentration.
- Consistent units.